Joining other weather teams, government forecasters on Wednesday called for a slower-than-normal hurricane season, adding fuel to the debate over whether the 20-year era of tropical intensity is finally drawing to an end.

In April, Phil Klotzbach and William Gray of Colorado State University called for seven named storms; AccuWeather predicts eight named storms while Tropical Storm Risk forecasts 11. The average six-month season produces 12 named storms, including six hurricanes.

All cite the emergence of El Niño, the large-scale weather pattern that suppresses storm formation by creating strong wind shear in the upper atmosphere for their predictions. Additionally, the temperature of tropical waters in the Atlantic are about normal.

President Barack Obama is using his annual hurricane briefing to warn that climate change will make these storms more intense and damaging.

While some climatic experts say the atmospheric conditions might be shifting toward a quieter phase, it would take at least three quiet storms seasons in a row for them to be convinced the intensity era is over.

So far, there have been two: 2013 saw only two Category 1 hurricanes; 2014 saw eight named storms, although six were hurricanes.

Phil Klotzbach, of Colorado State University, said cooler Atlantic waters combined with the past two relatively slow hurricane seasons "lend increased credence to the discussion that we may be ending the active era."

Here are the top 10 costliest hurricanes to hit the United States since 1980.

Here are the top 10 costliest hurricanes to hit the United States since 1980.

(Courtesy National Oceanic and Atmospheric Administration)

"It shouldn't be ruled out," he said.

But Gerry Bell, NOAA's lead hurricane forecaster, said the two main components that energize the intensity era – Atlantic sea surface temperatures and heavy rains in west Africa – show no signs of letting up.

Dan Kottlowski, senior meteorologist for AccuWeather, the online weather site, said there can be slow stretches within an intensity era and scientists likely won't know the era has ended until it actually has been over for a few years.

He said an intensity era usually lasts for 25 to 35 years, and we're now in year 20.

"In a nutshell, we are expecting Atlantic sea surface temperatures to remain warmer than normal this season and probably for the next few years," he said.

The current intensity era started in 1995 and since then, 14 seasons have been busy or extremely active, including tumultuous 2004 and 2005. In 2012, the most recent busy season, there were 10 hurricanes, including calamitous Sandy.

Most scientists believe the era is the result of a natural cycle of warming and cooling in the Atlantic and that it can switch from a warm to a cool phase within a matter of one or two years.

Yet, even in a cool phase, powerful hurricanes can develop, as was the case with Category 5 Hurricane Andrew, which hit South Florida in 1992, an otherwise calm period.

Florida has gone a record nine seasons without a hurricane strike, with the last one being Wilma in 2005. On average, the region is hit about once every six to seven years.

Sullivan, the NOAA administrator, said forecasters at the National Hurricane Center will benefit this season from an upgraded model and increased computer power.

"It has really sharpened the accuracy of track forecasts and has resulted in a five percent improvement in intensity forecasts, which have been a tough nut to crack for quite some time," she said.